session number	date	years since 1500	years since last
1	1582	82
2	1666	166	84
3	1730	230	64
4	1777	277	47
5	1820	320	43
6	1860	360	40
7	1890	390	30
8	1914	414	24
10	1938	438	24
11	1960	460	22
12	1984	484	24
13	2000	500	16